What is Atlantis?

Atlantis
is a part of a story by Plato which describes various forms of government.
In describing his ideal form of government in a theoretical Ancient Athens,
Plato mentions that it would be appropriate in his story for ancient
Athens to have defeated some worthy enemy in war, and in describing
a suitable enemy, he proposes to use a story which he says was originally
brought from Egypt. That was the story of Atlantis, an island larger than Libya and Asia combined
which lay in the Atlantic Ocean opposite the Pillars of Hercules, but which supposedly disappeared
into the sea in a day and night of earthquakes and floods.

The
Question is This:

Is any
part of Plato's description of Atlantis true, or was it entirely made
up?
Does any of it match a real place?
Let's see.